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We study global dynamical properties of the isometry group of the Borel randomization of a separable complete structure. In particular, we show that if properties such as the Rohklin property, topometric generics, extreme amenability hold…

Logic · Mathematics 2020-11-11 Alexander Berenstein , Rafael Zamora

In this paper we prove that isoperimetric sets in three-dimensional homogeneous spaces diffeomorphic to $\mathbb{R}^3$ are topological balls. We also prove that in three-dimensional homogeneous spheres isopermetric sets are either…

Differential Geometry · Mathematics 2015-02-17 Jih-Hsin Cheng , Andrea Malchiodi , Paul Yang

In the present paper, we show that many combinatorial and topological objects, such as maps, hypermaps, three-dimensional pavings, constellations and branched coverings of the two--sphere admit any given finite automorphism group. This…

Combinatorics · Mathematics 2020-01-16 Rémi Bottinelli , Laura Grave de Peralta , Alexander Kolpakov

For real hyperbolic spaces, the dynamics of individual isometries and the geometry of the limit set of nonelementary discrete isometry groups have been studied in great detail. Most of the results were generalised to discrete isometry…

Differential Geometry · Mathematics 2007-05-23 Gabriele Link

We prove definable versions of the Universal Coefficient Theorems of Eilenberg--Mac Lane expressing the (Steenrod) homology groups of a compact metrizable space in terms of its integral cohomology groups, and the (\v{C}ech) cohomology…

Algebraic Topology · Mathematics 2020-10-13 Martino Lupini

We use Fra\" iss\'e theoretic methods to construct several universal and ultrahomogeneous Polish metric structures. Namely, universal and ultrahomogeneous Polish metric space equipped with countably many closed subsets of its powers,…

Logic · Mathematics 2013-05-03 Michal Doucha

We prove an automatic convergence theorem for holomorphic modular forms on tube domains. The argument works in some generality, and covers in particular the case of orthogonal groups, symplectic groups, unitary and quaternion unitary…

Number Theory · Mathematics 2026-03-03 Aaron Pollack

Following the continuing interest in the Urysohn space and, more specifically, the recent problem area of finding and comparing group structures on the Urysohn space we prove that there exists a non-abelian group structure on the Urysohn…

General Topology · Mathematics 2018-02-09 Michal Doucha

We show that the topological full group of a Hausdorff ample groupoid with compact unit space coincides with the group of homotopy classes of invertible isometries in pseudofunction algebras associated with the groupoid. Moreover, if the…

Operator Algebras · Mathematics 2025-11-19 Eusebio Gardella , Mathias Palmstrøm , Hannes Thiel

We prove that if the shape of the metric unit ball in a homogeneous group enjoys a precise symmetry property, then the associated distance yields the standard form of the area formula. The result applies to some classes of smooth and…

Metric Geometry · Mathematics 2024-09-26 Francesca Corni , Valentino Magnani

We prove that every family of isospectral surfaces with discrete length spectrum arising from Sunada's method is finite. Furthermore, by introducing the topological notion of surfaces with self-duplicating ends, we show that every finite…

Geometric Topology · Mathematics 2026-02-24 Federica Fanoni , David Fisac

Motivated by Kloeckner's result on the isometry group of the quadratic Wasserstein space $\mathcal{W}_2\left(\mathbb{R}^n\right)$, we describe the isometry group $\mathrm{Isom}\left(\mathcal{W}_p (E)\right)$ for all parameters $0 < p <…

Metric Geometry · Mathematics 2024-08-19 György Pál Gehér , Tamás Titkos , Dániel Virosztek

Uniformly finite homology is a coarse invariant for metric spaces; in particular, it is a quasi-isometry invariant for finitely generated groups. In this article, we study uniformly finite homology of finitely generated amenable groups and…

Group Theory · Mathematics 2016-01-20 Matthias Blank , Francesca Diana

We prove a new kind of homological stability theorem for automorphism groups of finitely-generated projective modules over Dedekind domains, which takes into account all possible stabilisation maps between these, rather than only…

Commutative Algebra · Mathematics 2024-05-14 Oscar Randal-Williams

A topological space is reversible if each continuous bijection of it onto itself is open. We introduce an analogue of this notion in the category of topological groups: A topological group G is g-reversible if every continuous automorphism…

Group Theory · Mathematics 2019-12-24 Vitalij Chatyrko , Dmitri Shakhmatov

In this paper it is demonstrated that the Kasparov pairing is continuous with respect to the natural topology on the Kasparov groups, so that a KK-equivalence is an isomorphism of topological groups. In addition, we demonstrate that the…

Operator Algebras · Mathematics 2016-09-07 Claude Schochet

We prove that there exists a countable metrizable topological group $G$ such that every countable metrizable group is isomorphic to a quotient of $G$. The completion $H$ of $G$ is a Polish group such that every Polish group is isomorphic to…

Group Theory · Mathematics 2021-08-31 Vladimir G. Pestov , Vladimir V. Uspenskij

Let $\Aut(G)$ denote the group of (bi-)continuous automorphisms %and $\Out(G)$ the outer automorphism group of a non-Archimedean Polish group~$G$. We show that for any such $G$ with an invariant countable basis of open subgroups, the group…

Logic · Mathematics 2025-12-16 Andre Nies , Philipp Schlicht

We prove that every open $\sigma$-locally Polish groupoid $G$ is Borel equivalent to the groupoid of models on the Urysohn sphere $\mathbb{U}$ of an $\mathcal{L}_{\omega_1\omega}$-sentence in continuous logic. In particular, the orbit…

Logic · Mathematics 2019-08-12 Ruiyuan Chen

We study the synchronous and asynchronous automatic structures on the fundamental group of a graph of groups in which each edge group is finite. Up to a natural equivalence relation, the set of biautomatic structures on such a graph product…

Group Theory · Mathematics 2008-02-03 Walter D. Neumann , Michael Shapiro
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